Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$116.37	12.452%	$130.8604	$130.86	$130.85	$130.90
Purchase #2	$101.67	5.208%	$106.965	$106.97	$106.95	$107.00
Purchase #3	$128.26	11.107%	$142.5058	$142.51	$142.50	$142.50
Purchase #4	$28.65	4.215%	$29.8576	$29.86	$29.85	$29.90
Purchase #5	$65.87	9.722%	$72.2739	$72.27	$72.25	$72.30
Purchase #6	$134.95	3.436%	$139.5869	$139.59	$139.60	$139.60
Purchase #7	$171.49	4.287%	$178.8418	$178.84	$178.85	$178.80
7 purchase totals =	$747.26		$800.8914	$800.90	$800.85	$801.00